In the past, various methods have been used to make foam seat cushions which provide both support as well as a soft, comfortable seat. The methods of preparing such cushions for the most part have involved the bonding together with adhesives of different types of foams and/or foams of different hardnesses to form a laminated cushion having the desired properties. Such methods are effective, but they are time consuming and relatively expensive.
In the Ahrens U.S. Pat. No. 4,190,697, a method is disclosed for producing a multidensity foam article suitable for use as a seat cushion without using adhesives. In the patented method, a foam cushion having a firm, high density foam bottom layer and a soft, low density foam top layer is prepared by placing a first formulation capable of yielding a firm foam into a mold, permitting said formulation to start rising and foaming, pouring a second liquid formulation capable of forming a soft foam through the rising first formulation so that the first formulation floats upon the second formulation, and then permitting the two formulations to foam, rise and cure into a multidensity foam article in which the foam layers of different density are bonded and knitted together at their common boundaries.
In the McEvoy U.S. Pat. No. 4,405,681, a method is disclosed for producing a foam cushion comprised of three different firmnesses without using adhesives. The resulting cushion has a firm foam base, a soft foam top or seat and a border of foam of an intermediate firmness.
It is generally recognized that the ideal foam seat cushion would be a composite formed of multiple foams of different firmness and properties to best suit the anatomy of the expected user. The Ahrens and McEvoy methods and products are improvements over the prior art but a need still exists for a simple, fast, inexpensive method of preparing composite cushions having multiple areas of different firmness without piecing and glueing together pieces of foam.